Asymmetric cell division is a fundamental mechanism for differentiation and the generation of new cell types. The gram negative, alpha-proteobacterium Caulobacter crescentus follows an invarient pattern of unequal cell division to produce two progeny cells with different structures and developmental fates. This organism is now recognized as an ideal model system for the study of how cellular asymmetry is established and its role in developmental regulation. An understanding of these processes is the long-term goal of the research proposed in this application. Genetic analysis has shown that developmental events in these cells are tightly coordinated with cell cycle progression by networks of essential signal transduction pathways mediated by the two-component family of proteins. Remarkably, the sensor kinases that initiate these pathways are, like the morphogenic events they control, spatially localized at the cell poles. A central focus of the proposed work is to understand the molecular mechanisms responsible for the subcellular localization of the PleC, DivJ, DivL and CckA kinases and the role of localization in kinase function and regulation. The aims of the proposed experiments are to: (1) carry out a detailed genetic and biochemical analysis of the PleC kinase and its cognate essential response regulator DivK to define their roles in the regulation of polar morphogenesis and cell division; (2) identify the sequences within PleC and other cell cycle-regulated kinases that specify their subcellular localization and examine the role of localization in developmental regulation; and (3) identify elements of the cellular machinery responsible for subcellular localization of these signal transduction proteins.